1. Field of the Invention
The present invention relates to an improvement of alkaline storage batteries, particularly to an improvement of the structure of electrode assemblies suited for high electric current discharge at low temperature.
2. Description of Related Art
In recent years, with the strong trend toward lighter-weight and smaller-sized electric appliances, there has been an increasing demand for small-sized high capacity batteries as the power source therefor. Also in alkaline storage batteries, which are batteries with high reliability, in line with the above-mentioned trend, efforts have been made to increase the capacity of nickel-cadmium storage batteries or to develop and improve nickel-metal hydride storage batteries which use as the negative electrode hydrogen absorbing alloys having a high energy density. The alkaline storage batteries of this kind have a great advantage in that since the electrolyte thereof is an alkaline electrolyte of aqueous solution type, they can be charged and discharged at large electric currents.
These batteries are generally prepared by constructing a positive electrode plate and a negative electrode plate, with a separator interposed therebetween, into a spirally coiled electrode assembly, then welding current collectors to the respective end planes of the positive electrode plate and the negative electrode plate, housing the whole in a battery case, and then pouring a predetermined amount of an aqueous alkaline solution as the electrolyte into the case.
Previous nickel-metal hydride storage batteries, as compared with nickel-cadmium storage batteries, show a marked decrease of their discharge capacity when discharged at high electric currents, particularly at low temperatures.